Roughly ten other asteroids have passed as close or closer to the Earth as 2017 001 this year. Most of them are discovered shortly before they whizz by us. But astronomers are already anticipating the return of asteroid 2012 TC4, which is set to pass us at a distance more than twice as close as 2017 001 in October.

In the case of the plane-size asteroid, which was first seen by telescopes in Hawaii, it appears to be very dark or nonreflective, which probably made it harder to spot, according to NASA Solar System Ambassador Eddie Irizarry.

Also, space is a very large place filled with thousands of near-Earth asteroids. While many of them have been cataloged and are tracked, it seems we still don't have quite enough eyes, human or digital, to spot all of them.

First published July 27, 9:36 a.m. PT.Update, 4:40 p.m. PT:Adds more background on near-Earth asteroids.